BB&T agreed Wednesday to buy the $18.6 billion-asset Susquehanna for $2.5 billion in cash and stock, or roughly 169% of the Lititz, Pa., seller's tangible book value.

"This is not a deal you'd ever see us do," Davis said Wednesday during a question-and-answer session at a conference in New York hosted by Bank of America Merrill Lynch.

"It's both out-of-market and it's fairly expensive," Davis added. "We're going to stay in-market for transactions and branch-related deals and we're going to be as prudent and we can on cost."

Davis said his $391 billion-asset company is more interested adding to its payments and corporate trust businesses rather than pursuing whole-bank or branch transactions. Payments and corporate trust "continue to change the game on our diversification," Davis said. "They're low-capital users with high returns."

U.S. Bancorp has made one big M&A move so far this year, agreeing in June to pay about $315 million for more than 160 Chicago-area branches from Citizens Financial Group. Davis said that deal was a special case since it doubled the Minneapolis company's market share in Chicago. Barring such exceptional circumstances, Davis said the value of big, whole-bank transactions is limited.

"This company 10 years ago was the king of acquisitions for efficiency purposes," Davis said. "But I will tell you they are not as long-lived as a deal done for revenue. You get the scale, you get the efficiency, but you don't plate that more than one or two years out. Then, you've just got a bigger bank to do the same thing with."

U.S. Bancorp and BB&T have done one deal together. In January 2010, U.S. Bancorp paid BB&T an undisclosed sum for 14 branches in Nevada, along with $850 million of deposits. BB&T gained those branches after it bought the failed Colonial Bank from the Federal Deposit Insurance Corp. in 2009.